The production of semiconductor products often requires wet etching or some other form of wet processing of substrates that involves exposing the substrates to an aqueous-based liquid. After wet processing, the processing fluid and/or any aqueous-based rinsing fluid that remains on the surface of the substrate typically needs to be removed in order to prepare the substrate for the next processing step.
Generally speaking, the wet processing fluid and/or rinsing fluid may be removed by saturating the substrate with a drying fluid (DF) to displace the wet processing fluid. The drying fluid may be alcohol-based, for example, and may include surfactants and/or other adjuncts to maximize displacement efficiency. In order to avoid collapse of fragile structures on the substrate due to capillary forces, additional post-wet-processing step(s) may be performed to dry the substrate in a satisfactory manner.
As semiconductor features become smaller and smaller to accommodate higher device density requirements, there is a critical need for DF removal techniques that will prevent collapse of fragile structures and can satisfactorily dry out the wafer in as short a time as possible.
Supercritical CO2 has been investigated and employed to facilitate DF removal and avoid collapse of fragile structures on the substrate. CO2 at supercritical conditions (Tc=31 C, Tp=1070 psi) has no surface tension to initiate collapse from capillary forces, and good solubility for several potential drying fluids.
Existing DF removal processes utilizing supercritical CO2 have shown promising results toward preventing collapse of fragile structures, but often been time consuming, requiring a long time for DF agents and any other remaining residues to be satisfactorily removed. Existing DF removal processes using supercritical CO2 also require a large number of chamber turnovers to satisfactorily flush DF agents and any other remaining residues from the substrate surface, thereby undesirably increasing the total process time and volume of CO2 required, and reducing manufacturing productivity.
In view of the foregoing, improved supercritical CO2-based DF removal processes and apparatuses are desired.